Image forming apparatus

ABSTRACT

Disclosed is an image forming apparatus incorporating a discharging unit that discharges a printing medium outside the housing of the image forming apparatus, and which stacks the discharged printing medium. The discharging unit includes a discharging part arranged on the transportation path of the printing medium in the housing, a stacking lever rotatably supported on the housing and a driving unit that drives the stacking lever to rotate. The discharging part discharges a printing medium outside the housing, and stacks the discharged printing medium on a stacking unit provided outside the housing. The stacking lever guides the stacking of the printing medium in the stacking unit. A control unit may be provided to control the driving unit so as to vary the revolution position of the stacking lever based on the discharged position of the printing medium discharged by the discharging part.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No. 10-2009-0078410, filed on Aug. 24, 2009 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to an image forming apparatus, and more particularly, to an image forming apparatus employing a printing medium discharging unit capable of stably discharging and stacking printing media.

BACKGROUND OF RELATED ART

An image forming apparatus such as, for example, a printer, an electronic copier, a facsimile, a multifunction device and the like forms an image on a printing medium by one or more of various types of image forming processes, including, for example, an electrophotographic, an ink jet, a heat transfer, or the like. An image forming apparatus typically includes a discharging unit for discharging a printing medium on which an image has been formed.

In general, a discharging unit of an image forming apparatus may include among others a discharging roller provided on the discharging path of the printing medium, a stacker onto which the printing media are stacked and a stacking lever that guide the stacking of a printing medium discharged onto the stacker by the discharging roller. The stacking lever is typically rotatably disposed to a main body of the image forming apparatus, and reciprocally rotates by the force of a printing medium being discharged and by its own weight, allowing the stacking of the print media without requiring a separate driving force to downwardly press the printing medium.

In the discharging unit of the conventional image forming apparatus configured as described above, since the speed at which the movable end of the discharging lever descends by its own weight is slow, the stacked order of a printing medium may become out of the correct sequence in the case of a high speed discharging of printing media. That is, a sheet that is later in sequence may actually be stacked under the preceding sheet of printing medium. Further, the printing medium that is stacked out of order may prevent the printing medium that should have properly preceded it from being properly stacked so that the preceding printing medium may become turned over or may deviate from the stacker. Such improperly stacked printing medium may then prevent subsequent sheets of printing media from being discharged normally, and may even cause a jam.

SUMMARY OF DISCLOSURE

Accordingly to an aspect of the present disclosure, there may be provide an image forming apparatus that may include a housing, an image forming unit and a discharging unit. The image forming unit may be disposed in the housing, and may be configured to form an image on a printing medium. The discharging unit may be configured to discharge the printing medium outside the housing, and may be configured to stack the discharged printing medium. The discharging unit may comprise a discharging part disposed on the transportation path of the printing medium in the housing for discharging the printing medium outside the housing, a stacking unit on which printing media discharged outside the housing are stacked, a stacking lever which may be rotatably disposed in the housing, and which may be configured to guide stacking of the printing medium in the stacking unit, a driving unit configured to rotate the stacking lever and a control unit configured to control the driving unit so as to vary the revolution position of the stacking lever based on the discharged position of the printing medium being discharged by the discharging part.

The image forming apparatus may further comprise a discharging sensor disposed on the transportation path of the printing medium. The discharging sensor may be configured to sense the discharging position of the printing medium. The control unit may be configured to control the driving unit based on a sensing result of the discharging sensor.

The control unit may control the driving unit so that an end portion of the stacking lever maintains an ascending state when the leading end portion of the printing medium enters the stacking unit, and so that the end portion of the stacking lever descends when the trailing end portion of the printing medium enters the stacking unit.

The discharging part may comprise a discharging roller disposed on a first rotation shaft rotatably arranged on the printing medium transportation path and an idle roller formed on a second rotation shaft rotatably arranged on the printing medium transportation path, the second rotation shaft extending parallel to the first rotation shaft.

The stacking lever may comprise a revolution shaft disposed in the housing and a lever member rotatable about the revolution shaft, the lever member comprising an operating unit ascending and descending by the driving unit and a pressing unit configured to come into a pressing contact with the printing medium.

The pressing unit of the lever member may be formed to have at least one of a rectilinear shape, a rounded shape having a rounded end, a step shape and a bent shape bent toward the stacking unit as it extends away from the revolution shaft toward end of the pressing unit.

The stacking lever may comprise a second revolution shaft arranged in the housing, a second lever member rotatably disposed on the second revolution shaft and a link member. The second lever member may comprise a second operating unit interlocked with the operating unit of the lever member to ascend and descend therewith and a second pressing unit configured to come into a pressing contact with the printing medium in a pressing direction opposite to a direction in which the pressing unit of the lever member presses the printing medium. The link member may connect the operating unit of the lever member and the second operating unit of the second lever member.

The stacking lever may comprise a second revolution shaft arranged in the housing, a second lever member rotatably disposed on the second revolution shaft and a weight coupled to the second lever member. The second lever member may comprise a second pressing unit that may be configured to come into a pressing contact with the printing medium in a pressing direction opposite to a direction in which the pressing unit of the lever member presses the printing medium. The weight may bias the second pressing unit toward the pressing unit of the lever member by its own weight.

The driving unit may comprise a solenoid having an operating rod that ascends and descends by an electromagnetic force. The operating rod may be connected to an end portion of the stacking lever.

The driving unit may comprise a driving source configured to supply a rotation force, a cam member driven by the driving source to rotate and an elastic member elastically biasing the end of the stacking lever toward the cam member. The cam member may be configured to regulate the ascending height of an end of the stacking lever based on the rotational position of the cam member.

The stacking lever may comprise a revolution shaft arranged in the housing and a plurality of lever members disposed to the revolution shaft. The plurality of lever members may be arranged to be spaced apart from one another by a predetermined interval, and may respectively comprise an operating unit ascending and descending by the driving unit and a pressing unit pressing on the printing medium. The control unit may control the driving unit so that an end part of a lever member positioned in the central part of the printing medium in its widthwise direction among the plurality of lever members further descends in comparison to an end part of another lever member positioned at an edge part of the printing medium in the widthwise direction.

The driving unit may comprise a driving source configured to supply a rotational force, a plurality of cam members which are rotated by the rotational force supplied by the driving source and a plurality of elastic members. The plurality of cam members may be configured to regulate the ascending height of the operating unit of each of the plurality of lever members based on the rotation position of the plurality of cam members. The plurality of elastic members may elastically bias the operating unit of each of the plurality of lever members toward the cam members.

The driving unit may comprise a solenoid with an operating rod that ascends and descends by an electromagnetic force, an ascending/descending member which is interlocked with ascending and descending of the operating rod to thereby ascend and descend and a plurality of elastic members provided between the ascending/descending member and the operating unit of each of the plurality of lever members to elastically bias the operating unit of each of the plurality of lever members.

According to another aspect of the present disclosure, an image forming apparatus may be provided to include a housing, an image forming unit disposed in the housing for forming an image on a printing medium and a discharging unit configured to discharge the printing medium outside the housing. The discharging unit may stack discharged printing media, and may include an operating plate rotatably supported in the housing, a driving unit disposed in the housing for driving the operating plate to rotate, a discharging part supported on the operating plate for discharging the printing medium outside the housing, a stacking unit in which the printing medium discharged outside the housing by the discharging part is stacked, a stacking lever supported on the operating plate for guiding the stacking of the printing medium in the stacking unit based on the rotational position variation of the operating plate and a control unit which may control the driving unit so as to vary the revolution position of the stacking lever based on the discharged position of the printing medium being discharged by the discharging part.

The image forming apparatus may further comprise a discharging sensor disposed on the transportation path of the printing medium. The discharging sensor may be configured to sense the discharged position of the printing medium. The control unit may be configured to control the driving unit based on a sensing result of the discharging sensor.

The control unit may control the driving unit so that an end portion of the stacking lever maintains an ascending state when the leading end portion of the printing medium enters the stacking unit, and so that the end portion of the stacking lever descends when the trailing end portion of the printing medium enters the stacking unit.

The discharging part may comprise a discharging roller formed on a first rotation shaft supported on the operating plate and an idle roller formed on a second rotation shaft supported on the operating plate. The second rotation shaft may extend parallel to the first rotation shaft.

The operating plate may be configured to revolve about the first rotation shaft or about the second rotation shaft.

The driving unit may comprise a solenoid with an operating rod that ascends and descends by an electromagnetic force, and that is connected to a side of the operating plate.

The driving unit may comprise a driving source configured to supply a rotational force, a cam member that is driven to rotate by the rotational force supplied by the driving source and an elastic member. The cam member may be configured to regulate the revolution position of an end of the operating plate based on the rotation position of the cam member. The elastic member may be configured to elastically bias the end of the operating plate toward the cam member.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features and advantages of the present disclosure will become apparent and more readily appreciated from the following description of several embodiments thereof, taken in conjunction with the accompanying drawings, of which:

FIG. 1 is a schematic sectional view illustrating an image forming apparatus according to an embodiment of the present disclosure;

FIG. 2 is a partial sectional perspective view illustrating a discharging unit according to an embodiment of the present disclosure;

FIGS. 3 and 4 schematically illustrate operation states of the discharging unit of FIG. 2;

FIGS. 5 and 6 schematically illustrate the operation of the lever member of the discharging unit of FIG. 2;

FIG. 7 schematically illustrates a discharging unit according to another embodiment of the present disclosure;

FIG. 8 is a schematic perspective view illustrating a discharging unit according to another embodiment of the present disclosure;

FIG. 9 schematically illustrates the operational state of the discharging unit of FIG. 8;

FIG. 10 schematically illustrates a discharging unit according to another embodiment of the present disclosure;

FIG. 11 is a schematic perspective view illustrating a discharging unit according to another embodiment of the present disclosure;

FIG. 12 schematically illustrates the bent shape of printing media by a pressing unit of a lever member of the discharging unit of FIG. 11;

FIG. 13 is a schematic perspective view illustrating a discharging unit according to another embodiment of the present disclosure;

FIG. 14 is a schematic perspective view illustrating a discharging unit according to another embodiment of the present disclosure;

FIG. 15 schematically illustrates operational state of the discharging unit of FIG. 14; and

FIG. 16 schematically illustrates a discharging unit according to another embodiment of the present disclosure.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

Reference will now be made in detail to several embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout, repetitive descriptions of which may be omitted for brevity sake. It should be also noted that in the drawings, the dimensions of the features are not intended to be to true scale and may be exaggerated for the sake of allowing greater understanding.

FIG. 1 is a schematic sectional view illustrating an image forming apparatus according to an embodiment of the present disclosure.

Referring to FIG. 1, an image forming apparatus according to an embodiment may include a housing 1, an image forming unit 10 disposed inside the housing 1 for forming an image on printing media M and a discharging unit 100 for discharging the printing medium M outside the housing 1.

The image forming apparatus may further include a printing medium supplying unit 30 mounted to the housing 1 for supplying the printing medium M. The printing medium supplying unit 30 may be detachably provided to an inner portion and/or to an outer portion of the housing 1, and may supply the printing medium M to the image forming unit 10. The printing medium M supplied through the printing medium supplying unit 30 is transported toward the image forming unit 10 through a transportation path 41.

According to an embodiment, the supplying unit 30 may include a first supplying unit 31 used for an automatic supplying of the printing medium M and a second supplying unit 35 used for a manual supplying. The first supplying unit 31 may be provided inside the housing 1, and may supply the printing medium M by the rotation of a first pickup roller 33. The second supplying unit 35 may be disposed outside the housing 1, and may supply the printing medium M to the transportation path 41 by the rotation of a second pickup roller 37.

The transportation path 41 may be provided inside the housing 1. The printing medium M supplied from the printing medium supplying unit 30 may be transported along the transportation path 41. To that end, the transportation path 41 may include a plurality of transporting rollers 43 and 45. According to an embodiment, in the transportation path 41, the path through which the printing media are supplied from the first and second supplying units 31 and 35 diverges into two paths while the remaining path for the forming of image and for discharging the printing media is provided as a single path. The image forming apparatus may further include a plurality of sensors S1 and S2 for sensing the transportation position of a printing medium being transported on the transportation path 41.

The image forming unit 10 forms an image on the printing medium M supplied from the supplying unit 30 along the transportation path 41 through a predetermined image forming process such as an electrophotographic type, a heat transfer type, an inkjet type, or the like. The image forming apparatus according to an embodiment shown in FIG. 1 is example of an image forming apparatus employing the electrophotographic type image forming unit 10.

As shown in FIG. 1, according to an embodiment, the image forming unit 10 may include a developing unit 11, a light scanning unit 23 forming an electrostatic latent image, a transferring unit 21 transferring an image formed in the developing unit 11 onto a printing medium and a fusing unit 25 fusing the image transferred to the printing medium M. The developing unit 11 may include a toner container 11 a in which toner T of a predetermined color is accommodated, a photosensitive medium 13 on which the electrostatic latent image is formed by the light beam L from the light scanning unit 23, a charging unit 15 charging the photosensitive medium 13 to a predetermined electric potential, a developing roller 17 arranged to face the photosensitive medium 13 for developing using toner T the electrostatic latent image on the photosensitive medium 13 into a developed image and a supply roller 19 for supplying the toner T to the developing roller 17. The light scanning unit 23 scans a light onto the photosensitive medium 13 to form the electrostatic latent image on the photosensitive medium 13. The transferring unit 21 may be disposed to face the photosensitive medium 13 between which the printing medium M transported through the transportation path 41 is to be interposed, and may perform the process transferring the developed image formed to the photosensitive medium 13 to a supplied printing medium M. The image transferred to the printing medium M by the transferring unit 21 is fused onto the printing medium M by the fusing unit 25.

To that end, the fusing unit 25 may include a heat source 26, a heating roller 27, a surface of which is heated by the heat generated by the heat source 26, a temperature sensor (not shown) measuring a surface temperature of the heating roller 27 and a fusing control unit (not shown) controlling the electrical power supplied to the heat source 26 based on the surface temperature of the heating roller 27 measured by the temperature sensor.

While in the above-described embodiment(s) the image forming unit 10 is described as an electrophotographic type image forming unit, but the image forming unit 10 may employ any other types of image forming processes, including, for example, an ink jet type or a heat transferring type. In addition, while, for the sake of brevity, in FIG. 1 a monochromatic electrophotographic image forming unit that employs toner of single color is depicted, according to alternative embodiments, a color electrophotographic color image forming unit of either a multi pass type or a single pass type known to those skilled in the art that utilizes a plurality of color toners may be employed.

Hereinafter, a discharging unit 100 according to several embodiments of the present disclosure will be described in references to FIGS. 2 to 16.

FIG. 2 is a partial sectional perspective view illustrating a discharging unit 100 according to an embodiment of the present disclosure. FIGS. 3 and 4 schematically illustrate the operational states of the discharging unit of FIG. 2.

Referring to FIGS. 1-4, the discharging unit 100 according to an embodiment may include a discharging part 110 discharging a printing medium M, a stacking unit 120 in which the discharged printing media M are stacked, a stacking lever 130, a driving unit 150 for rotating the stacking lever 130 and a control unit 170.

The discharging part 110 is disposed on a printing medium transportation path 41 inside the housing 1, and discharges the printing medium M outside the housing 1. The stacking unit 120 is a space in which the printing media M discharged outside the housing 1 are stacked. The stacking lever 130 may be supported on the housing 1 in such a manner it is capable of rotating reciprocally, and guides the stacking of the printing media on the stacking unit 120.

The control unit 170 controls the driving unit 150 so that the rotation position of the stacking lever 130 varies depending on the discharged position of the printing medium M being discharged by the discharging part 110.

According to an embodiment, the discharging unit 100 may further include a discharging sensor 180 disposed on the transportation path 41 for sensing the discharging of the printing medium M. In such embodiment, the control unit 170 controls the driving unit 150 based on the sensing result of the discharging sensor 180. That is, as shown in FIG. 3, the control unit 170 controls the driving unit 150 so that the end part 139 a (see FIG. 4) of the stacking lever 135 maintains an ascending state if the leading end portion of the printing medium M enters the stacking unit 120. As shown in FIG. 4, the control unit 170 controls the driving unit 150 so that the end part 139 a descends when the trailing end portion of the printing medium M enters the stacking unit 120.

The discharging part 110 may include a discharging roller 111 and an idle roller 113. The discharging roller 111 is supported on the first rotation shaft 111 a disposed on the transportation path 41. The idle roller 113 is supported on the second rotation shaft 113 a disposed on the transportation path 41 parallel with the first rotation shaft 111 a.

The discharging roller 111 and the idle roller 113 may each include a plurality of rollers supported respectively on the first and second rotation shafts 111 a and 113 a spaced apart from one another by a predetermined interval. With such configuration, each of the discharging rollers 111 may be arranged to face a respective corresponding one of the idling rollers 113 or may be arranged between two idling rollers 113.

The stacking lever 130 may include a revolution shaft 131 rotatably supported by the housing 1 and a lever member 135 supported on the revolution shaft 131 so as to rotate with the revolution shaft 131. The lever member 135 may include an operating unit 137 that ascends and descends by the driving unit 150 and a pressing unit 139 that comes into a contact with a printing medium M being discharged.

According to an embodiment, the lever member 135 may be configured as a pressing unit 139 having a rectilinear shape as shown in FIG. 2, as a pressing unit having a rounded shape in which an end part 139 a is rounded as shown in FIG. 3, as a pressing unit 239 having its end portion bent toward the stacking unit 120 as shown in FIG. 5, or a pressing unit 339 having a stepped shape as shown in FIG. 6.

According to an embodiment, the driving unit 150 may include a solenoid 151 with an operating rod 151 a that ascends and descends by an electromagnetic force, and which is connected to the operating unit 137 of the stacking lever 130. With such configuration, the lever member 135 moves with the ascending and descending of the operating rod 151 a to thereby pivot about the revolution shaft 131.

FIG. 7 schematically illustrates a discharging unit according another embodiment according to the present disclosure. Referring to FIG. 7, the driving unit 150 may be configured as a cam driving unit 155. The cam driving unit 155 may include a driving source 156 supplying a rotation force, a cam member 157 and an elastic member 159. The cam member 157 is driven by the driving source 156, and regulates an ascending height of the operating unit 137 of the lever member 135. The elastic member 159 may be provided to elastically bias the operating unit 137 toward the cam member 157. With the above configuring the driving unit 150, the pivoting of the lever member 135 about the revolution shaft 131 can be actively controlled. Accordingly, the trailing end portion of a printing medium M can be pressed when the trailing end portion of the printing medium is discharged to the stacking unit 120, and the printing medium M can be stacked more rapidly in comparison to a conventional lever member that operate by its own weight. Further, by returning back the rotational position of the lever member 135 to the ascended position before the discharging of the subsequent printing medium, the lever member 135 can be prevented from interfering with the leading end portion of the subsequent printing medium.

FIG. 8 is a schematic perspective view illustrating a discharging unit according to another embodiment of the present disclosure whereas FIG. 9 schematically illustrates the operational states of the discharging unit of FIG. 8.

Referring to FIGS. 8 and 9, according to an embodiment, the stacking lever 130 may include a first revolution shaft 131 disposed to the housing 1, a first lever member 135 rotatably disposed to the first revolution shaft 131, a second revolution shaft 144, a second lever member 145 and a link member 142. The first lever member 135 includes a first operating unit 137 ascending and descending by the driving unit 150 and a first pressing unit 139 pressing a printing medium.

The discharging unit according to the present embodiment has the distinction of further including the second revolution shaft 144, the second lever member 145 and the link member 142 in comparison to the discharging unit according to the previously described embodiments.

The second lever member 145 is supported on to the second revolution shaft 141, and includes a second operating unit 147 linked with the first operating unit 137 by the linking member 142 to ascend and descend and a second pressing unit 149 pressing the printing medium from the opposite direction to the pressing direction of the first pressing unit 139. The link member 142 connects the first operating unit 137 and the second operating unit 147, and transmits the driving force supplied from the driving unit 150 to the second lever member 145.

With the configuration described above, by supporting the printing medium M being discharged to the stacking unit 120 from the upper and lower directions, downward sagging of the leading end of the next printing medium can be prevented, thereby guiding the next printing medium to be stacked from a higher position than the trailing end of the preceding printing medium. Accordingly, the out of sequence stacking of the subsequent printing medium being inserted under the preceding printing medium can be prevented.

FIG. 10 schematically illustrates a discharging unit according to another embodiment of the present disclosure.

Referring to FIG. 10, according to an embodiment, a stacking lever 130 may include a first revolution shaft 131 rotatably supported on the housing 1, a first lever member 135 rotatably disposed to the first revolution shaft 131, a second revolution shaft 141, a second lever member 145 and a weight 144. The discharging unit according to the embodiment has a distinction of including the weight 144 instead of the link member 142 of the previous embodiment of FIG. 8.

The weight 144 is disposed to the second lever member 145, and biases the second pressing unit 149 toward the first pressing unit 139. Accordingly, when the first pressing unit 139 ascends and descends by the driving unit 150, the weight 144 ascends and descends by the pressing force of the first pressing unit 139 and by its own weight to support the lower side of the printing medium.

FIG. 11 is a schematic perspective view illustrating a discharging unit according to another embodiment of the present disclosure. FIG. 12 schematically illustrates the bent shape of a printing medium imparted by the pressing unit of the lever member in FIG. 11.

Referring to FIGS. 11 and 12, a stacking lever 130 of the discharging unit according to an embodiment may include a revolution shaft 131 rotatably supported on the housing 1 and a plurality of lever members 135 coupled to the revolution shaft 131 and spaced apart from one another by a predetermined distance interval. Each of the plurality of lever members 135 may include an operating unit 137 ascending and descending by the driving unit 150 and a pressing unit 139 for pressing a printing medium M.

With such configuration, the control unit 170 controls the driving unit 150 so that an ends of the lever members 135 b and 135 c positioned in the central part in the widthwise direction of the discharged printing medium M among the plurality of lever members 135 further descends in comparison to the ends of the lever members 135 a and 135 d positioned at an edge part in the widthwise direction of the printing medium M when the rear end part of the printing medium M enters the stacking unit 120.

To that end, the driving unit 150 may include a driving source 156, a cam rotation shaft 158, a plurality of cam members 157 a through 157 d supported on the cam rotation shaft 158 to be spaced apart from one another by a predetermined interval and a cam driving unit 155 that may include a plurality of elastic members 159 a through 159 d. The plurality of cam members 157 a, 157 b, 157 c and 157 d rotate by the driving source 156, and regulates an ascending height of the operating unit 137 of the respective corresponding one of lever members 135 a, 135 b, 135 c and 135 d depending on the rotation position. The plurality of elastic members 159 a, 159 b, 159 c and 159 d elastically bias the operating unit 137 of the respective corresponding one of lever members 135 a, 135 b, 135 c and 135 d toward the cam members 157 a, 157 b, 157 c and 157 d, respectively.

With the above described configuration, the present embodiment varies the revolution angles of the plurality of lever members as shown in FIG. 12 so that the air between the printing medium currently being discharged and the printing medium discharged immediately subsequently is allowed to escape when the printing medium descends to the stacking unit. Accordingly, the turning over of a printing medium, the position deviation and the reversed stacking order of the printing media caused by the air resistance during the stacking process can be prevented.

FIG. 13 is a schematic perspective view illustrating a discharging unit according to another embodiment of the present disclosure.

Referring to FIG. 13, the stacking lever 130 of the discharging unit according to an embodiment may include a revolution shaft 131 rotatably supported on the housing 1 and a plurality of lever members 135 coupled to rotate with the revolution shaft 131 and spaced apart from one another by a predetermined interval. Each of the plurality of lever members 135 includes an operating unit 137 that ascends and descends by the driving unit 150 and a pressing unit 139 for pressing a printing medium M. In comparison to the previously described embodiments, there is a distinction that the driving unit 150 according to the present embodiment is changed. That is, the driving unit 150 includes a solenoid 151 driving an operating rod 151 a to ascend and descend by an electromagnetic force, an ascending/descending member 152 interlocked with the ascending and descending of the operating rod 151 a, and a plurality of elastic members 153 a, 153 b, 153 c and 153 d. The elastic members 153 a, 153 b, 153 c and 153 d are provided between the ascending/descending member 152 and the operating unit 137 of each of lever member 135 a, 135 b, 135 c and 135 d to elastically bias the operating unit 137 of each lever member 135 a, 135 b, 135 c and 135 d, respectively.

The plurality of elastic members 153 a, 153 b, 153 c and 153 d may have different elastic coefficients or lengths. For example, the elastic members 153 b and 153 c disposed to the central part may have larger elastic coefficients or longer lengths than the elastic members 153 a and 153 d disposed at the edge portion. Accordingly, when the trailing end of the printing medium M enters the stacking unit 120, the ends of the lever members 135 b and 135 c positioned at the central part in the widthwise direction of the discharged printing medium can further descend in compassion to the ends of the lever members 135 a and 135 d positioned at the edge part in the widthwise direction of the printing medium.

FIG. 14 is a schematic perspective view illustrating a discharging unit according to another embodiment of the present disclosure while FIG. 15 schematically illustrates the operational states of the discharging unit of FIG. 14.

Referring to FIGS. 14 and 15, the discharging unit according to the present embodiment may include an operating plate 201 rotatably disposed inside the housing 1, a driving unit 250 for rotatably driving the operating plate 201, a discharging part 210, a stacking unit (not shown) in which a printing medium discharged outside the housing 1 is stacked, a stacking lever 230 and a control unit 270. The operating plate 201 is supported on the housing 1 rotatably about a revolution shaft 205, and is rotated by the driving unit 250.

The discharging part 210 is also supported on the operating plate 201, and discharges a printing medium outside the housing 1. The discharging part 210 may include a discharging roller(s) 211 formed on a first rotation shaft 211 a supported on the operating plate 201, and an idle roller(s) 213 formed on a second rotation shaft 213 a also supported on the operating plate 201 parallel with the first rotation shaft 211 a. Accordingly, the discharging part 210 can change the discharging direction of a printing medium discharged between the discharging roller 211 and the idle roller 213 depending on the rotational position of the operating plate 201.

The stacking lever 230 supported on the operating plate 201 guides the stacking of the printing medium on the stacking unit by varying its position depending on variation of the rotational position of the operating plate 201.

The control unit 270 controls the driving unit 250 to vary the revolution position of the stacking lever 230 depending on the discharging position of the printing medium being discharged in the discharging part 210. That is, the control unit 270 controls the driving unit 250 so that the printing medium pressing end part of the stacking lever 230 can maintain an ascending state when the leading end portion of the printing medium enters the stacking unit. The control unit 270 further controls the driving unit 250 so that the printing medium pressing end part of the stacking lever 230 can descend when the trailing end portion of the printing medium enters the stacking unit.

The discharging unit according to an embodiment may further include a discharging sensor 280 disposed along the printing media transportation path, which may sense the discharging of a printing medium. In such an embodiment, the control unit 270 may control the driving unit 250 based on the sensing result of the discharging sensor 280.

The driving unit 250 may include a solenoid 251 including an operating rod that extends and retracts by an electromagnetic force, and that is connected to a side of the operating plate 201. Alternatively, the driving unit 250 may include a cam driving unit including a driving source, a cam member and an elastic member. The cam driving unit may have the substantially same configuration as the cam driving unit of the discharging unit according to the embodiment described in reference to FIG. 7.

As described above, by proving the discharging part 210 and the stacking lever 230 to the operating plate 201 that is rotationally driven, the positions of the discharging roller 211 and the idle roller 213 configuring the discharging part 210 and the position of the stacking lever 230 can be actively controlled, thereby efficiently preventing the stacking errors.

FIG. 16 schematically illustrates a discharging unit according to another embodiment of the present disclosure.

As shown in FIG. 16, the discharging unit according to an embodiment may have the distinction of providing the revolution shaft 205 of the operating plate 201 to be coaxial with the first rotation shaft 211 a or the second rotation shaft 213 a. In the example shown in FIG. 16 illustrates an example of the operating plate 201 rotating about the second rotation shaft 213 a. With such a configuration, although the operating plate 201 rotates about the second, rotation shaft 213 a of the idle roller 213, since the rotational shaft of the idle roller 213 does not vary, there is the advantage that it is not necessary to change the configuration and the disposition of the driving force transmitting unit if the rotational driving force is transmitted to the idle roller from an external driving source.

While a detailed structure of the control unit 150 or 250 is not depicted in the figures herein, as would be readily understood by those skilled in the art, the control unit may be, e.g., a microprocessor, a microcontroller or the like, that includes a CPU to execute one or more computer instructions to implement the various control operations herein described and/or control operations relating to other components of the image forming apparatus, such as, for example, one or more of the print medium supply device 30, the image forming unit 10, and, to that end, may further include a memory device, e.g., a Random Access Memory (RAM), Read-Only-Memory (ROM), a flesh memory, or the like, to store the one or more computer instructions.

The image forming apparatus according to the embodiments described above provides a driving unit rotating a stacking lever to actively control the revolution of the stacking lever depending on the discharging state of a printing medium. Accordingly, the printing medium can be stably stacked even when discharging printing media at a high speed.

According to one or more aspects of the present disclosure, and according to one or more embodiments described herein, the revolution angles of the a plurality of stacking levers disposed along the widthwise direction of a printing medium may be controlled independently so as to allow the air between two consecutively discharged printing media to escape. Accordingly, the turning over or the position deviation of a printing medium caused by the air friction can be reduced.

According to one or more aspects of the present disclosure, an operating plate rotatably disposed to a housing, and on which the discharging roller(s), the idle roller(s), as well as the stacking lever(s) are supported, may be provided to thereby change the discharging direction of a printing medium being discharged between the discharging roller and the idle roller. According to such embodiments, the position of the operating plate may be controlled depending on the discharging position of the printing medium, thereby realizing a more stable discharging and stacking of printing media.

While the present disclosure has been particularly shown and described with reference to several embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made thereto without departing from the principles and spirit of the present disclosure, the proper scope of which is defined in the following claims and their equivalents. 

1. An image forming apparatus, comprising: a housing; an image forming unit disposed in the housing, the image forming apparatus being configured to form an image on a printing medium; and a discharging unit configured to discharge the printing medium outside the housing, and to stack a discharged printing medium, the discharging unit comprising: a discharging part disposed on a printing medium transportation path in the housing, the discharging part being configured to discharge the printing medium outside the housing; a stacking unit on which printing media discharged outside the housing are stacked; a stacking lever which is rotatably disposed in the housing, the stacking lever being configured to guide stacking of the printing medium in the stacking unit; a driving unit configured to rotate the stacking lever; and a control unit configured to control the driving unit so as to vary a revolution position of the stacking lever based on a discharged position of the printing medium being discharged by the discharging part.
 2. The image forming apparatus according to claim 1, further comprising a discharging sensor disposed on the printing medium transportation path, the discharging sensor being configured to sense the discharging position of the printing medium, wherein the control unit is configured to control the driving unit based on a sensing result of the discharging sensor.
 3. The image forming apparatus according to claim 2, wherein the control unit controls the driving unit so that an end portion of the stacking lever maintains an ascending state when a leading end portion of the printing medium enters the stacking unit, and so that the end portion of the stacking lever descends when a trailing end portion of the printing medium enters the stacking, unit.
 4. The image forming apparatus according to claim 1, wherein the discharging part comprises: a discharging roller disposed on a first rotation shaft rotatably arranged on the printing medium transportation path, and an idle roller formed on a second rotation shaft rotatably arranged on the printing medium transportation path, the second rotation shaft extending parallel to the first rotation shaft.
 5. The image forming apparatus according to claim 1, wherein the stacking lever comprises: a revolution shaft disposed in the housing, and a lever member rotatable about the revolution shaft, the lever member comprising an operating unit ascending and descending by the driving unit and a pressing unit configured to come into a pressing contact with the printing medium.
 6. The image forming apparatus according to claim 5, wherein the pressing unit of the lever member is formed to have at least one of a rectilinear shape, a rounded shape having a rounded end, a step shape and a bent shape bent toward the stacking unit as it extends away from the revolution shaft toward end of the pressing unit.
 7. The image forming apparatus according to claim 5, wherein the stacking lever comprises: a second revolution shaft arranged in the housing, a second lever member rotatably disposed on the second revolution shaft, the second lever member comprising a second operating unit interlocking with the operating unit of the lever member to ascend and descend therewith and a second pressing unit configured to come into a pressing contact with the printing medium in a pressing direction opposite to a direction in which the pressing unit of the lever member presses the printing medium, and a link member which connects the operating unit of the lever member and the second operating unit of the second lever member.
 8. The image forming apparatus according to claim 5, wherein the stacking lever comprises: a second revolution shaft arranged in the housing, a second lever member rotatably disposed on the second revolution shaft, the second lever member comprising a second pressing unit configured to come into a pressing contact with the printing medium in a pressing direction opposite to a direction in which the pressing unit of the lever member presses the printing medium, and a weight coupled to the second lever member, the weight biasing the second pressing unit toward the pressing unit of the lever member by its own weight.
 9. The image forming apparatus according to claim 1, wherein the driving unit comprises a solenoid having an operating rod that ascends and descends by an electromagnetic force, the operating rod being connected to an end portion of the stacking lever.
 10. The image forming apparatus according to claim 1, wherein the driving unit comprises: a driving source configured to supply a rotation force, a cam member driven by the driving source to rotate, the cam member being configured to regulate an ascending height of an end of the stacking lever based on a rotational position of the cam member, and an elastic member elastically biasing the end of the stacking lever toward the earn member.
 11. The image forming apparatus according to claim 1, wherein the stacking lever comprises: a revolution shaft arranged in the housing, and a plurality of lever members disposed to the revolution shaft spaced apart from one another by a predetermined interval, and respectively comprise an operating unit ascending and descending by the driving unit, and a pressing unit pressing on the printing medium, and wherein the control unit controls the driving unit so that an end part of a lever member positioned in a central part of the printing medium in its widthwise direction among the plurality of lever members further descends in comparison to an end part of another lever member positioned at an edge part of the printing medium in the widthwise direction.
 12. The image forming apparatus according to claim 11, wherein the driving unit comprises: a driving source configured to supply a rotational force, a plurality of cam members which are rotated by the rotational force supplied by the driving source, the plurality of cam members being configured to regulate an ascending height of the operating unit of each of the plurality of lever members based on a rotation position of the plurality of cam members, and a plurality of elastic members which elastically bias the operating unit of each of the plurality of lever members toward the cam members.
 13. The image forming apparatus according to claim 11, wherein the driving unit comprises: a solenoid with an operating rod that ascends and descends by an electromagnetic force, an ascending/descending member which is interlocked with ascending and descending of the operating rod to thereby ascend and descend, and a plurality of elastic members provided between the ascending/descending member and the operating unit of each of the plurality of lever members to elastically bias the operating unit of each of the plurality of lever members.
 14. An image forming apparatus, comprising: a housing; an image forming unit disposed in the housing, the image forming apparatus being configured to form an image on a printing medium; and a discharging unit configured to discharge the printing medium outside the housing, and to stack discharged printing media, the discharging unit comprising: an operating plate rotatably supported in the housing; a driving unit disposed in the housing, the driving unit being configured to drive the operating plate to rotate; a discharging part supported on the operating plate, the discharging part being configured to discharge the printing medium outside the housing; a stacking unit in which the printing medium discharged outside the housing by the discharging part is stacked; a stacking lever supported on the operating plate, the stacking lever being configured to guide stacking of the printing medium in the stacking unit based on a rotational position variation of the operating plate; and a control unit which controls the driving unit to vary a revolution position of the stacking lever based on a discharged position of the printing medium being discharged by the discharging part.
 15. The image forming apparatus according to claim 14, further comprising a discharging sensor disposed on a transportation path of the printing medium, the discharging sensor being configured to sense the discharged position of the printing medium, wherein the control unit is configured to control the driving unit based on a sensing result of the discharging sensor.
 16. The image forming apparatus according to claim 14, wherein the control unit controls the driving unit so that an end portion of the stacking lever maintains an ascending state when a leading end portion of the printing medium enters the stacking unit, and so that the end portion of the stacking lever descends when a trailing end portion of the printing medium enters the stacking unit.
 17. The image forming apparatus according to claim 14, wherein the discharging part comprises: a discharging roller which formed on a first rotation shaft supported on the operating plate, and an idle roller formed on a second rotation shaft supported on the operating plate, the second rotation shaft extending parallel to the first rotation shaft.
 18. The image forming apparatus according to claim 17, wherein the operating plate is configured to revolve about the first rotation shaft or about the second rotation shaft.
 19. The image forming apparatus according to claim 14, wherein the driving unit comprises a solenoid with an operating rod that ascends and descends by an electromagnetic force, the operating rod being connected to a side of the operating plate.
 20. The image forming apparatus according to claim 14, wherein the driving unit comprises: a driving source configured to supply a rotational force; a cam member which is driven to rotate by the rotational force supplied by the driving source, the cam member being configured to regulate a revolution position of an end of the operating plate based on a rotation position of the cam member, and an elastic member configured to elastically bias the end of the operating plate toward the cam member. 